Catalytic Enantioselective (3+2) Annulations of Nucleophilic Thioacyl Rh(I)-Carbenes with Achmatowicz Rearrangement Products

Abstract

The cycloaddition and annulation reactions of Achmatowicz rearrangement products (ARPs) are critically important to the construction of molecular complexity and the total synthesis of natural products. However, this field is still blemished by the shortage of enantioselective (3+2) reactions of ARPs. Herein, we report the highly enantio-, diastereo-, and regioselective (3+2) annulations of ARPs with nucleophilic αthioacyl Rh(I)-carbenes under Rh(I)/(R)-BINAP catalysis, producing bicyclic dihydrothiophenes with multiple functionalities, three continuous chiral centers, and five prochiral centers in up to 97% yields and 99:1 er. Mechanistically, the migratory insertion following anticoordination is suggested to determine the enantio-and regioselectivities and accounts for the nucleophilic character of α-thioacyl Rh(I)-carbenes. DFT calculations revealed that enantioinduction originates from the steric discrimination of (R)-and (S)-ARPs by the chiral ligand.